Project Summary/Abstract Many researchers over the past 75 years have found a clear link between dietary intake/metabolism and long- term health and disease. Dietary restriction (DR), defined as a decrease in caloric intake without malnutrition, remains the most potent and reproducible intervention to improve health and longevity across multiple species. Unfortunately, long-term DR is both relatively untested and very difficult to implement in humans, leading researchers to better define the mechanisms through which DR improves health in an effort to mimic the benefits in the absence of true DR. This project focuses on a family of xenobiotic metabolizing enzymes, flavin-containing monooxygenases, or FMOs, that are induced downstream of DR and were recently reported to be both necessary and sufficient to increase health, stress resistance, and longevity in the nematode C. elegans. Interestingly, previous reports also show induction of FMO homologs in mammalian systems under DR and other conditions known to increase longevity. Unfortunately, the mechanism(s) for the effects of these well-conserved FMO proteins on health and longevity are largely unknown, as their primary role in phase I xenobiotic detoxification is not clearly linked to the observed effects on health and longevity. This project will explore the endogenous role and substrates of FMO proteins by developing and utilizing important tools for measuring their metabolic effects and enzyme-specific activities. Focusing on the latest metabolomics technology, the project will 1) develop a novel food source for nematodes to better measure their metabolism on and off xenobiotic compounds, 2) develop a metabolomics based technique to use oxygen isotopes and identify substrates of oxygenases, 3) identify and validate candidate endogenous substrates for nematode FMO proteins, and 4) test whether the nematode endogenous substrates are also substrates of mammalian FMO proteins. To ensure their success, these assays will be performed by experts in nematode and mammalian biology and aging in collaboration with experts in metabolomics profiling and data analysis. The resulting data will provide important tools for nematode biologists measuring the metabolic impact of genetic and environmental perturbations that can effect both worm and bacterial biology and for biochemists looking for new ways to characterize enzymatic substrate profiles. In addition, the results focused on FMO protein activity will produce foundational data for publications and award applications based on understanding and exploiting the mechanism(s) of FMO activity and their role modifying health and longevity.